North Queensland Cowboys are keeping a close eye on the Michael Jennings saga, with Penrith rumoured to be preparing a big money play for Johnathan Thurston.

Johnathan Thurston - pictured on his first day at the North Queensland Cowboys back in 2004 - could leave them for an NRL record $5.2m deal. Source: The Courier-Mail

THE Cowboys are fighting to retain Johnathan Thurston with Sydney rivals, headed by Penrith, putting together packages that will see the Test playmaker attract an NRL record $5.2 million deal.

Having navigated an Australian Crime Commission doping probe, the Cowboys are now locked in a fresh battle to secure Thurston as the Panthers and Canterbury ramp up their pursuit of the Queensland five-eighth.

Souths ace Greg Inglis set a salary benchmark when he signed a five-year upgrade worth $4 million last September.

The cashed-up Panthers are a major threat to North Queensland's hopes of keeping the 29-year-old.

In total, Thurston can command a four-year package worth $1.3 million a season by moving south, which would place him in the same earnings stratosphere as AFL stars Gary Ablett, Buddy Franklin, Chris Judd and Tom Scully.

A Sydney-based official last night told The Courier-Mail the money on offer for Thurston will make him the richest player the code has seen.

"We are talking in the vicinity of $5 million. It is going to be a big number," the executive said. "But we'd be mad not to have a crack at him. This could be his last contract so Johnathan naturally wants as many years as he can get.

"The truth is Johnathan is an incumbent player at the Cowboys and in the market we're in, players don't ordinarily leave clubs if they are happy.

"I think Thurston is happy at North Queensland but the big bonus for any Sydney club is the scope for third-party opportunities."

Thurston's manager Sam Ayoub said he had yet to receive any formal offers but NRL suitors can now table firm packages after the completion of Collective Bargaining Agreement negotiations last week.

NRL clubs now have clarity on what they can afford to pay elite players under the salary cap for the next five seasons.

It is understood Penrith have discussed a multi-year deal, of between three to four seasons, worth an estimated $900,000 annually under the salary cap.

Thurston is eligible for an additional $400,000-$500,000 via third-party agreements and a Marquee Player Allowance, which is capped at $600,000 for each club this season before an incremental rise to $750,000 by 2017.

Cowboys coach Neil Henry said his "gut feeling" was Thurston would stay in North Queensland but he conceded a massive offer from a rival club would be difficult for the player to resist.

"You can't take away from the fact that if another club come racing in with a significantly bigger offer, because they can as they are chasing a one-off player, then that is an attractive offer," Henry said.

"It is the same with all our players. Parramatta are chasing Matt Scott and if they want to get him, their offer is always going to be more competitive than ours because we are trying to sign three or four players.

"But I think JT will stay. He has a very strong bond with his mates up here."

Ayoub added that his primary objective is to investigate the post-career opportunities for Thurston.

"I need to find the right club and the right post-football opportunities for Johnathan," he said.

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